Technical Field
The present disclosure relates generally to an anvil assembly having a tiltable head which is suitable for use with a circular anastomosis stapler. More specifically, the present disclosure relates a tiltable anvil assembly having an improved retaining mechanism.
Background of Related Art
Circular anastomosis staplers which include an anvil assembly having a tiltable anvil head are known in the art. An example of such circular anastomosis stapler and tiltable anvil assembly are disclosed in commonly owned U.S. Pat. No. 7,364,060 (“the '060 patent”). A further example of a tiltable anvil assembly is disclosed in commonly owned U.S. Pat. No. 8,540,132 (“the '132 patent”). The content of each of the '060 patent and the '132 patent are incorporated herein by reference in their entirety. The anvil assembly described in the '132 patent includes a backup member located within the anvil assembly positioned to prevent tilting of the anvil head of the anvil assembly prior to firing of the stapler, e.g., in a proximal position. Upon firing of the stapler, a knife blade of the stapler engages and moves the backup member to a position, e.g., a distal position, which allows the anvil head to tilt upon retraction of the knife blade. If the backup member sticks to the knife blade upon retraction of the knife blade and/or is otherwise not retained in the distal position, the backup member may return to the proximal position, thereby preventing the anvil head from tilting.
In order to maintain the backup member in the proximal position where it prevents tilting of the anvil head prior to firing, the anvil assembly described in the '132 patent includes a retainer member positioned distal of the backup member. The retainer member includes a plurality of deformable tabs which prevent distal movement of the backup member until a predetermined force sufficient to deform the tabs is applied to the backup member, i.e., through engagement with the knife blade during staple formation. A residual proximal force is produced during deformation of the deformable tabs. This force acts on the backup member which may cause the backup member to move proximally towards its original position. As described in the '132 patent, the tilting operation of the anvil assembly relies on the distal positioning of the backup member following the firing of the stapler. Any proximal force that acts on the backup member may cause the backup member to return to the original proximal position, thereby preventing tilting of the anvil assembly.
Therefore, it would be beneficial to provide an anvil assembly with a mechanism or feature for retaining the backup member in the proximal position prior to firing of the stapling assembly, that allows the backup member to move to the distal position during firing of the stapling assembly, and that retains the backup member in the distal position after firing of the stapling assembly such that the anvil assembly may tilt.